This study investigated the production patterns of vowel epenthesis/deletion in Korean learners’ English contrasts of /ʧ/ vs. /ʧi/ and /ʤ/ vs. /ʤi/ in word-final position, where such errors are frequently observed among the learners. Through a production experiment of 20 pairs of English words contrastive in word-final vowel, a total of 800 tokens were obtained from 20 Korean learners of English of high and low proficiency levels. The results revealed that the learners exhibited phonological processes of vowel epenthesis or deletion and that multiple factors such as voicing of a preceding consonant, frequencies of target words and learners’ proficiency in target language were involved. Voicing of a final palato-alveolar affricate played an important role in vowel epenthesis. With regard to vowel deletion, learners with low proficiency levels showed the influence of voicing of a palato-alveolar affricate by deleting the vowel /i/ more frequently after the voiceless /ʧ/ than after the voiced /ʤ/. Overall, the vowel epenthesis error seems to be motivated by L1 phonology while vowel deletion error was influenced by word frequencies. Further acoustic analysis revealed that higher-level learners’ epenthetic vowels, when compared to lexical vowels, exhibited significant differences with regard to vowel ratio and F1 while the low-level learners’ did not.

This study investigated L2 production, perception, and the relation of production and perception by examining 20 Korean learners’ production and perception of the English contrasts of /ʃ/ vs. /ʃi/, /ʧ/ vs. /ʧi/, and /ʤ/ vs. /ʤi/ in word final position. Of the 20 Korean learners, 10 (5 males, 5 females) were low in English proficiency and the other 10 (5 males, 5 females) were high. Our findings from production and perception experiments showed that the relation of L2 production and perception varies according to learners’ proficiency levels in L2. A significant correlation between L2 production and perception was attested within the high group learners. Thus, the high group learners with higher production accuracy generally exhibited higher perception accuracy. Unlike the high group, the low group learners’ production and perception patterns did not show any significant correlation between the two. In general, the low group displayed higher accuracy in production than in perception. In addition, within the low group, the heavy influence of L1 constraints on L2 perception was attested while L2 production was not in accordance with L1 phonology.

This study investigated the influence of L1-specific constraints on L2 perception. In particular, we examined the effect of the unreleased coda constraint in L1 on Korean learners’ perception of word final palatal sibilants across two proficiency levels, i.e., low vs. high. Our findings from a perception experiment showed that Korean learners, especially the low group learners, tended to hear the illusory vowel /i/ after a word final palatal sibilant. Thus, the low group learners had a difficulty in discriminating the contrasts of /ʃ/ vs. /ʃi/, /ʧ/ vs. /ʧi/, and /ʤ/ vs. /ʤi/. According to the perception experiment, the low group learners’ illusory vowel perception rates increased as frication noise of the word final palatal sibilant got longer. Additionally, the low group learners were not influenced by the relative duration of the vowel /i/ in perceiving the vowel. Rather, their vowel responses were more likely to be influenced by the frication duration of a word final palatal sibilant. The study revealed that L1 constraints are significant factors influencing L2 perception.